COQ8A encodes an atypical protein kinase essential for coenzyme Q10 (CoQ10) biosynthesis, a critical lipid-soluble electron transporter required for aerobic cellular respiration 1. The protein's catalytic mechanism remains incompletely defined: it may phosphorylate COQ3 protein or act as a lipid kinase targeting prenyl lipid intermediates in the ubiquinone biosynthesis pathway, with unusual selectivity for ADP over ATP binding 2. Pathogenic COQ8A variants cause primary CoQ10 deficiency-4 (COQ10D4), characterized by early-onset cerebellar ataxia with multisystem involvement including dystonia, epilepsy (32%), cognitive impairment (49%), and exercise intolerance 3. Clinical presentation exhibits remarkable heterogeneity; some patients present with prominent dystonia and writing difficulties rather than ataxia 4, while cerebellar atrophy is universal on MRI 3. Disease progression is mild-to-moderate (0.45 SARA points/year), but CoQ10 supplementation response is inconsistent—only approximately half of patients achieve notable clinical improvement 5, with cerebellar bioenergetic state potentially predicting treatment response 6. Additionally, elevated COQ8A expression has been associated with increased major depressive disorder risk through mitochondrial dysfunction 7.